Oxygen Atmosphere On A Tiny World.

[daniel l.]

I'm currently working on a story, and I'm getting to a part that involves a 16km wide rocky body with a core made of an alien substance that is of an extremely high mass, thus increasing the object's gravity at the surface to 1g.

My question is: can it sustain a breathable oxygen atmosphere at surface level? What would the characteristics of such an atmosphere be?

The object has plenty of plants to replenish the air.

[Hypercosmic]

I imagine that the core is a small black hole.

Note: The object is 16 km wide, meaning that its radius is 8 km, and the gravity is 1g (9.81 m/s²). Its mass is therefore a little less than 1e+19 kg. According to this calculator, if the core is actually a small black hole, it will produce a constant energy of 0.000003563442 W, glows at the temperature of 12272.03 K, and without feeding it, it'll stay around for 2.664132e+33 years.

I don't think that with such a small, low-mass body, you can just dump air to make the surface pressure high enough for humans to breath, and even if it is possible to do that, the air will keep escaping your tiny object because the escape velocity is really low. It's still a small, low-mass body, after all. After a while, you'll found that a significant amount of air has escaped.

The best way to fix this is to make a shell around the whole object AKA paraterraform it.

Edited December 14, 2017 by Hypercosmic

[Daveroski]

Like any world with an atmosphere regardless of gravity, you need a method to hold the atmosphere in place.

If the technology is there a magnetic bottle would do the job. It's alien tech so a couple of ideas about where the power might be originating, a singularity or a parallel universe tap or some-such.

Even then, when the 'world' moves the atmosphere would lag behind it causing winds which would not only be uncomfortable but raise questions about surface erosion and such.. So keeping it's orientation stable would be the way to go.

The alien magnetic bottle could 'sense' if an object tying to pass through it was 'powered' or not. Allowing 'powered' object to pass through freely while acting as a shield to non-powered objects. Or perhaps only objects with methane oxygen and carbon dioxide  could be 'sensed' and allowed passage.

 

[DAL59]

 

 

[wumpus]

You might want to consider a hollow planet (pretty much any idea has to be artificial and has significant issues.  Hollow planets would require less "tech levels" than most others.

I'm surprised that I haven't seen an analysis of Kerbal's atmosphere in the years I've been on this forum (maybe I just missed it).  I have no idea how much oxygen and nitrogen Earth loses each million years or so, but would have thought it was significant.  I guess it isn't: while there is plenty of oxygen locked up in the ocean and rocks, I'm less sure where nitrogen could be hiding.  I suspect Kerbal has roughly the same oxygen partial pressure (slowly being grabbed from sources) and no significant nitrogen.

[PB666]

i have to say the Mega Earths it probably the worst.

One of the problem of using black holes and in particular galactic black holes is that it like building a dartboard planet, the stars close by in eccentric orbits being the darts. We have actually watch our GBH eat stars and watch other GBH belch X-rays generated by stars being eaten.

[Gaarst]

No. Atmospheric O2 has average velocities of about 400 m/s, which is about equal to the escape velocity on such a body. So you wouldn't even need a sun to lose all your atmosphere very quickly.

[ProtoJeb21]

4 hours ago, Hypercosmic said:

I imagine that the core is a small black hole.

Note: The object is 16 km wide, meaning that its radius is 8 km, and the gravity is 1g (9.81 m/s²). Its mass is therefore a little less than 1e+19 kg. According to this calculator, if the core is actually a small black hole, it will produce a constant energy of 0.000003563442 W, glows at the temperature of 12272.03 K, and without feeding it, it'll stay around for 2.664132e+33 years.

Still not as bad as what will happen when you collapse an Interdictor-class Star Destroyer into a black hole. It lasts less than an hour, but could potentially eradicate half the galaxy. 

[Hypercosmic]

16 hours ago, ProtoJeb21 said:

Still not as bad as what will happen when you collapse an Interdictor-class Star Destroyer into a black hole. It lasts less than an hour, but could potentially eradicate half the galaxy. 

Nah, I don't think that the explosion would be significant or even noticeable to the rest of the galaxy at all. Also, judging by the damned thing's size, a black hole made form it should last a million years at least.

19 hours ago, wumpus said:

You might want to consider a hollow planet (pretty much any idea has to be artificial and has significant issues.  Hollow planets would require less "tech levels" than most others.

I'm surprised that I haven't seen an analysis of Kerbal's atmosphere in the years I've been on this forum (maybe I just missed it).  I have no idea how much oxygen and nitrogen Earth loses each million years or so, but would have thought it was significant.  I guess it isn't: while there is plenty of oxygen locked up in the ocean and rocks, I'm less sure where nitrogen could be hiding.  I suspect Kerbal has roughly the same oxygen partial pressure (slowly being grabbed from sources) and no significant nitrogen.

Earth loses 96,600 tons of hydrogen and helium every year. That's 96.6e9 kg/year. Earth's total mass is 6e24 kg. At that rate it will take a really long time to deplete all hydrogen in the atmosphere. Not so long for helium though.

Kerbin's atmosphere probably loses more, but most likely not significant over a short period of time.

19 hours ago, PB666 said:

i have to say the Mega Earths it probably the worst.

One of the problem of using black holes and in particular galactic black holes is that it like building a dartboard planet, the stars close by in eccentric orbits being the darts. We have actually watch our GBH eat stars and watch other GBH belch X-rays generated by stars being eaten.

You don't have to, and shouldn't, build shells around existing black holes, because they're too massive. You can, and should, create your own black hole.